A SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial, its preparation method and application

Abstract

This invention relates to a SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial, its preparation method, and its application. The SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial has a core-shell structure with ZnO-NH2 quantum dots as the core and SiO2 as the shell; wherein the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial has a hexagonal wurtzite structure, a particle size distribution of 2.25–5.25 nm, and an average particle size of 3.39 ± 0.03 nm.

Description

Technical Field

[0001] This invention belongs to the field of nano-fluorescent materials and seawater dissolved oxygen detection technology, specifically relating to a SiO2@ZnO-NH2 quantum dot nano-fluorescent material, its preparation method, and its application. Background Technology

[0002] Dissolved oxygen concentration is a crucial indicator for assessing seawater quality and pollution levels, and it serves as an important basis for research on water body self-purification capacity, marine ecological environment assessment, and marine scientific experiments. A dissolved oxygen level of 5–6 mg / L is essential for the normal survival of fish. When dissolved oxygen levels drop below 2 mg / L, fish growth is significantly inhibited; below 1 mg / L, fish stop feeding; and when dissolved oxygen levels further fall below 0.5 mg / L, fish die within a very short time. Therefore, in-situ monitoring of seawater dissolved oxygen helps to quickly reflect the survival conditions of aquatic organisms and is of great significance to the development of marine aquaculture.

[0003] Currently, most dissolved oxygen sensors utilize oxygen-sensitive fluorescent materials, which are fluorescent films composed of fluorescent indicators and carriers immobilizing the fluorescent substances. Commonly used fluorescent indicators include polycyclic aromatic hydrocarbon organic dyes, transition metal polypyridine compounds, and noble metal complexes. Ruthenium metal complexes, discovered in 1986 to be sensitive to oxygen molecules in fluorescence intensity and possessing advantages such as long fluorescence duration, high sensitivity, and large Stokes shift, remain the most widely used fluorescent indicator. However, organic-based fluorescent indicators suffer structural damage and reduced stability under the high salinity and strong currents of seawater. For example, the YSI EXO multi-parameter water quality analyzer, after only one month of continuous testing at sea, exhibited a 40.78% data shift. Therefore, there is an urgent need to develop an inorganic oxygen-sensitive fluorescent material to improve the stability of dissolved oxygen sensors under the conditions of high salinity and strong currents in seawater. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a SiO2@ZnO-NH2 quantum dot nanofluorescent material, its preparation method, and its application.

[0005] In a first aspect, the present invention provides a SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial, wherein the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial has a core-shell structure with ZnO-NH2 quantum dots as the core layer and SiO2 as the shell layer; wherein the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial has a hexagonal wurtzite structure, a particle size distribution of 2.25-5.25 nm, and an average particle size of 3.39±0.03 nm.

[0006] Preferably, the fluorescence emission of the SiO2@ZnO-NH2 quantum dot nanofluorescent material is located at 550–560 nm.

[0007] Secondly, the present invention provides a method for preparing the above-mentioned SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial, the preparation method comprising the following steps:

[0008] (1) Dissolve the alkali in anhydrous ethanol to obtain an ethanol solution of the alkali; dissolve zinc acetate in anhydrous ethanol and transfer it to an ice-water bath for cooling to obtain an ethanol solution of zinc acetate.

[0009] (2) Add the ethanol solution of alkali dropwise to the ethanol solution of zinc acetate and stir until the mixed solution is clear to obtain a ZnO quantum dot solution;

[0010] (3) Add 3-aminopropyltriethoxysilane aqueous solution to ZnO quantum dot solution and stir continuously. By controlling the amino functionalization process, SiO2 coating is achieved on the surface of the fluorescent material. After centrifugation and washing, the SiO2@ZnO-NH2 quantum dot nanofluorescent material is obtained.

[0011] Preferably, the alkali is potassium hydroxide, sodium hydroxide, or lithium hydroxide; more preferably, the purity of the alkali is ≥95%.

[0012] Preferably, the alkali is dissolved in anhydrous ethanol by ultrasonic-assisted dissolution; more preferably, the ultrasonic power is 80-100W and the ultrasonic time is 0.5-2 hours.

[0013] Preferably, the purity of the zinc acetate is ≥99.995%; the zinc acetate is dissolved in anhydrous ethanol by heating and reflux, the heating and reflux temperature is 60-80°C, and the heating and reflux time is 20-40 minutes;

[0014] Preferably, the time for transferring zinc acetate dissolved in anhydrous ethanol to an ice-water bath for cooling is controlled to be 1 to 5 minutes.

[0015] Preferably, the mass ratio of alkali to anhydrous ethanol in the alkali ethanol solution is controlled to be (0.098-0.13):1, more preferably 0.124:1; the mass ratio of zinc acetate to anhydrous ethanol in the zinc acetate ethanol solution is controlled to be (0.03-0.05):1, more preferably 0.046:1; and the amount ratio of the alkali ethanol solution to the zinc acetate ethanol solution is controlled to be 3.4-3.552g:0.7-24.8g, more preferably 3.4-3.5g:0.7-1.2g.

[0016] Preferably, the volume ratio of deionized water to APTEs in the 3-aminopropyltriethoxysilane aqueous solution is controlled to be 5:1; and the volume ratio of 3-aminopropyltriethoxysilane aqueous solution to ZnO quantum dot solution is controlled to be (0.018-0.7):1, preferably 0.07:1.

[0017] Preferably, the 3-aminopropyltriethoxysilane aqueous solution is added to the ZnO quantum dot solution and stirred continuously for 20 to 30 minutes; the centrifugation speed is 6000 to 10000 rpm and the centrifugation time is 3 to 10 minutes, preferably 5 minutes.

[0018] Thirdly, the present invention provides an application of the above-mentioned SiO2@ZnO-NH2 quantum dot nanofluorescent material in the detection of dissolved oxygen concentration in seawater.

[0019] Beneficial effects

[0020] (1) This invention is the first to apply SiO2@ZnO-NH2 quantum dot nanofluorescent material to the detection of dissolved oxygen in seawater;

[0021] (2) The SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials provided by this invention can exist stably in an alkaline environment and can resist the presence of macroelements (Cl-, Na-) in seawater. + K + Mg 2+ 、Sr 2+ F - ,Br - Ca 2+ SO4 2- HCO3 - The erosion of B) is simple, efficient and economical, and can be prepared on a large scale;

[0022] (3) The SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials prepared in this invention have a significant response to the dissolved oxygen concentration (0-20 mg / L) in seawater. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the preparation process of SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials.

[0024] Figure 2 The fluorescence emission spectrum of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1 under 365nm excitation;

[0025] Figure 3 The XRD pattern of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1;

[0026] Figure 4 (a) Photographs of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials prepared in Example 1 under fluorescent and ultraviolet light (pH = 6.80–10.26). Figure 4 (b) The fluorescence emission spectrum of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1 under 365 nm excitation (pH = 6.80–10.26);

[0027] Figure 5 (a) Photographs of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials prepared in Example 1 dispersed in different ion concentrations under fluorescent and ultraviolet lamps; Figure 5 (b) The fluorescence emission spectra of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1 dispersed in different ion concentrations under 365 nm excitation;

[0028] Figure 6 The response spectrum of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1 to the dissolved oxygen concentration in seawater;

[0029] Figure 7 The fluorescence emission spectrum of the ZnO quantum dot nanofluorescent material prepared without APTEs in Comparative Example 1 under 365 nm excitation is shown.

[0030] Figure 8 The XRD pattern of the ZnO quantum dot fluorescent nanomaterial prepared in Comparative Example 1 without the addition of APTEs is shown.

[0031] Figure 9 Photographs of ZnO quantum dot fluorescent nanomaterials prepared without APTEs in Comparative Example 1 within the pH range of 6.80–10.26 (under UV light irradiation);

[0032] Figure 10 Photographs of ZnO quantum dot fluorescent nanomaterials prepared without APTEs in Comparative Example 1 dispersed in solutions with different ion concentrations under UV light irradiation;

[0033] Figure 11 The fluorescence emission spectrum of the ZnO-NH2-a quantum dot fluorescent nanomaterial prepared in Comparative Example 2 under 365 nm excitation is shown.

[0034] Figure 12 The XRD pattern of the ZnO-NH2-a quantum dot fluorescent nanomaterial prepared in Comparative Example 2 is shown below.

[0035] Figure 13The image shows the fluorescence emission spectrum (excitation wavelength 365 nm) of the ZnO-NH2-a quantum dot fluorescent nanomaterial prepared in Comparative Example 2 in the pH range of 6.8 to 10.26. The inset is a photograph under ultraviolet light irradiation.

[0036] Figure 14 The image shows the ZnO-NH2-a quantum dot fluorescent nanomaterials prepared in Comparative Example 2 dispersed in solutions with different ion concentrations under a UV lamp. Detailed Implementation

[0037] The present invention is further illustrated by the embodiments described below. It should be understood that the embodiments described below are for illustrative purposes only and are not intended to limit the present invention.

[0038] First, this invention provides a SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial, wherein the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial has a core-shell structure with ZnO-NH2 quantum dots as the core layer and SiO2 as the shell layer; wherein the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial has a hexagonal wurtzite structure, a particle size distribution of 2.25-5.25 nm, and an average particle size of 3.39±0.03 nm.

[0039] In some embodiments, the fluorescence emission of the SiO2@ZnO-NH2 quantum dot nanofluorescent material is located at 550-560 nm.

[0040] The fluorescence emission of ZnO mainly originates from the transition from oxygen vacancy defects to zinc vacancy defects. Under high oxygen partial pressure, oxygen molecules enter oxygen vacancies and recombine with them, leading to a decrease in the luminescence intensity associated with oxygen vacancy defects. The higher the oxygen vacancy concentration, the stronger the response to dissolved oxygen.

[0041] The following is an exemplary description of a method for preparing SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials provided by the present invention. The preparation method may include the following steps.

[0042] (1) Preparation of ethanol solutions of alkali and zinc acetate. The alkali is dissolved in anhydrous ethanol to obtain an ethanol solution of alkali; zinc acetate is dissolved in anhydrous ethanol and transferred to an ice-water bath for cooling to obtain an ethanol solution of zinc acetate.

[0043] In some embodiments, the alkali may be potassium hydroxide, sodium hydroxide, or lithium hydroxide; preferably, the purity of the alkali is ≥95%.

[0044] In some embodiments, the alkali can be dissolved in anhydrous ethanol by ultrasonic-assisted dissolution; preferably, the ultrasonic power can be 80-100W and the ultrasonic time can be 0.5-2 hours.

[0045] In some embodiments, the purity of the zinc acetate is ≥99.995%; preferably, the zinc acetate can be dissolved in anhydrous ethanol by heating and reflux, the heating and reflux temperature can be 60-80°C, and the heating and reflux time can be 20-40 minutes.

[0046] Preferably, the cooling time after zinc acetate is dissolved in anhydrous ethanol and transferred to an ice-water bath can be controlled to be 1–5 minutes. Cooling ensures the normal growth of ZnO after the subsequent addition of alkaline solution. If the solution temperature is too high, the nanocrystals will grow too quickly, causing them to agglomerate and precipitate; if the solution temperature is too low, the solubility of zinc acetate will be low. Furthermore, excessively long cooling times can easily lead to the formation of recrystallized particles.

[0047] (2) Preparation of ZnO quantum dot solution. Add the ethanol solution of alkali dropwise to the ethanol solution of zinc acetate and stir for 20-30 minutes until the mixed solution is clear to obtain ZnO quantum dot solution.

[0048] In some embodiments, the mass ratio of alkali to anhydrous ethanol in the alkali ethanol solution can be controlled to be (0.098–0.13):1, preferably 0.124:1; the mass ratio of zinc acetate to anhydrous ethanol in the zinc acetate ethanol solution can be controlled to be (0.03–0.05):1, preferably 0.046:1; the ratio of the amount of alkali ethanol solution to zinc acetate ethanol solution can be controlled to be 3.4–3.552 g: 0.7–24.8 g, preferably 3.4–3.5 g: 0.7–1.2 g. Excessive alkali solution dosage will lead to a decrease in the fluorescence emission intensity of the generated ZnO.

[0049] The formation process of ZnO quantum dot nanofluorescent materials mainly involves three steps: (1) Zinc acetate dissolved in ethanol solvent is hydrolyzed to obtain ZnO. 2+ and CH3COO - The base undergoes an ionization reaction to produce OH-. - (2) When an ethanol solution of alkali is added dropwise to an ethanol solution of zinc acetate, the Zn ionized in the solution... 2+ and OH - A collision occurs, leading to a series of reactions that generate Zn(OH)4. 2- Unit; (3) Under the influence of ion diffusion and collisions between molecules and ions, Zn(OH)4 2-The units aggregate together through a dehydration reaction to form ZnO quantum dot fluorescent nanomaterials. The reaction process of alkali with zinc acetate is: Zn(CH3COO)2 + 2KOH → ZnO + H2O + 2KCH3COO. In the formation of ZnO quantum dot fluorescent nanomaterials, the raw material ratio and reaction temperature are key factors affecting the material properties. Excessively high temperatures cause the ZnO quantum dot fluorescent nanomaterials to grow too rapidly, leading to the aggregation of nanoparticles, which in turn results in a decrease in fluorescence intensity and stability.

[0050] (3) Preparation of SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials. An aqueous solution of 3-aminopropyltriethoxysilane (APTEs) was added to the ZnO quantum dot solution and stirred continuously. SiO2 coating on the surface of the fluorescent material was achieved by controlling the amino functionalization process. After centrifugation and washing, SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials were obtained.

[0051] In some embodiments, the volume ratio of deionized water to APTEs in the 3-aminopropyltriethoxysilane (APTEs) aqueous solution can be controlled to be 5:1; the volume ratio of APTEs aqueous solution to ZnO quantum dot solution can be controlled to be (0.018-0.7):1, preferably 0.07:1. If the amount of APTEs is too small, the SiO2 coating thickness will be insufficient, leaving some ZnO-NH2 quantum dot fluorescent nanomaterials exposed, which is insufficient to resist the high concentration of Cl in seawater. - This can lead to aggregation fluorescence quenching of nanofluorescent materials; excessive use of APTEs will result in material waste and increase preparation costs.

[0052] In some embodiments, the APTEs aqueous solution is added to the ZnO quantum dot solution and stirred continuously for 20 to 30 minutes.

[0053] In some embodiments, the centrifugation speed can be 6000 to 10000 rpm, and the centrifugation time can be 3 to 10 minutes, preferably 5 minutes.

[0054] This invention obtains SiO2-encapsulated SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials through surface modification with SiO2 and -NH2 groups. On one hand, the presence of -NH2 enhances the stability of the quantum dots and increases fluorescence intensity; on the other hand, SiO2, acting as a shell, not only increases the stability of the inorganic nanoparticles but also prevents the formation of Cl- in seawater. - Fluorescence aggregation quenching caused by interaction with fluorescent nanocrystals.

[0055] This invention prepares SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials using the sol-gel method. The surface of the fluorescent material is optimized by an amino functionalization strategy. By controlling the amino functionalization process and reaction temperature, the fluorescence performance of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials is improved. It has the advantages of simple process, low raw material cost, high production efficiency, economy and environmental protection, and can be mass-produced.

[0056] The quantum dots obtained by the preparation method provided in this invention can exist stably in an alkaline environment. A solution was prepared in deionized water to simulate the ionic environment of seawater, based on the concentrations of common elements in seawater. The results show that the fluorescence emission intensity of the SiO2@ZnO-NH2 quantum dot nanomaterials is unaffected and can resist the presence of common elements (Cl) in seawater. - Na + K + Mg 2+ 、Sr 2 + F - ,Br - Ca 2+ SO4 2- HCO3 - The erosion of B).

[0057] The SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial provided by this invention has a significant response to dissolved oxygen concentration (0-20 mg / L) in seawater and can be used in the field of dissolved oxygen concentration detection technology in seawater.

[0058] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention fall within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0059] Example 1

[0060] The preparation method of SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials provided by this invention includes the following steps:

[0061] (1) Weigh the raw materials according to the mass ratio of potassium hydroxide to anhydrous ethanol of 0.124:1 and place them in a glass beaker for ultrasonic dissolution for 1.5 hours; weigh the raw materials according to the mass ratio of zinc acetate to anhydrous ethanol of 0.046:1 and place them in a three-necked flask. Set the heating temperature to 78°C and heat, stir and reflux for 30 minutes. After the zinc acetate is completely dissolved in anhydrous ethanol, quickly place it in a cold water bath to cool for 5 minutes to obtain the ethanol solution of potassium hydroxide and the ethanol solution of zinc acetate.

[0062] (2) Add potassium hydroxide solution dropwise to zinc acetate solution, and control the ratio of potassium hydroxide ethanol solution to zinc acetate ethanol solution to be 3.552g:24.8g. Stir continuously for 30 minutes until the solution is clear to obtain ZnO quantum dot solution.

[0063] (3) Measure 0.4 mL of APTEs solution and add it to 2 mL of deionized water to prepare APTEs aqueous solution. Then add it to 34 mL of the above ZnO quantum dot solution and stir continuously. The SiO2 coating on the surface of the fluorescent material is achieved by controlling the amino functionalization process. The material is centrifuged and washed three times with anhydrous ethanol at a speed of 8000 rpm and a centrifugation time of 5 minutes to obtain SiO2@ZnO-NH2 quantum dot nanofluorescent material.

[0064] Figure 1 This is a schematic diagram of the preparation process of SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials.

[0065] The anti-interference ability and dissolved oxygen in seawater of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials prepared in Example 1 were tested. An alkaline buffer solution was prepared using potassium hydroxide to test the stability of the SiO2@ZnO-NH2 quantum dot aqueous solution.

[0066] Different concentrations of Cl were prepared according to the standard seawater salinity S = 35‰. - Na + K + Mg 2+ 、Sr 2+ F - ,Br - Ca 2+ SO4 2- HCO3 - The stability of the SiO2@ZnO-NH2 quantum dot nanofluorescent material aqueous solution was tested by adding the SiO2@ZnO-NH2 quantum dot nanofluorescent material aqueous solution to the above solutions with different ion concentrations.

[0067] Seawater samples were subjected to centrifugation, filtration, boiling (30 minutes), and re-filtration to remove impurities and microorganisms. 1 mL of an aqueous solution of SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial was added to the treated seawater. The dissolved oxygen content was controlled by adjusting the oxygen / nitrogen ratio to investigate the response characteristics of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial to dissolved oxygen in seawater.

[0068] Figure 2 The image shows the fluorescence emission spectrum of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1 under 365 nm excitation. As can be seen from the image, the fluorescence emission peak of the SiO2@ZnO-NH2 quantum dots is located at 553 nm.

[0069] Figure 3 The image shows the XRD pattern of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1. As can be seen from the image, the diffraction peaks of the amino-functionalized SiO2@ZnO-NH2 quantum dots are consistent with the standard XRD pattern of hexagonal wurtzite zinc oxide (JCPDS NO. 36-1451), and an aminopropylsiloxane diffraction peak appears at approximately 23°, indicating the successful synthesis of amino-functionalized ZnO quantum dots.

[0070] Figure 4 (a) Photographs of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials prepared in Example 1 under fluorescent and ultraviolet light (pH = 6.80–10.26). Figure 4 (b) The fluorescence emission spectrum of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1 under 365 nm excitation (pH = 6.80–10.26). As can be seen from the figure, the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial can exist stably in an alkaline environment, and its fluorescence emission intensity is not affected.

[0071] Figure 5 (a) Photographs of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials prepared in Example 1 dispersed in different ion concentrations under fluorescent and ultraviolet lamps; Figure 5 (b) The fluorescence emission spectra of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials prepared in Example 1, dispersed in different ion concentrations, under 365 nm excitation. As can be seen from the figure, the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterials maintain bright fluorescence emission under different ion concentrations, and the intensity of its fluorescence emission peak is not affected. This indicates that SiO2, as a shell, can increase the stability of inorganic nanoparticles and also prevent Cl... - Fluorescence aggregation quenching caused by interaction with fluorescent nanocrystals.

[0072] Figure 6 The figure shows the response spectrum of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial prepared in Example 1 to the dissolved oxygen concentration in seawater. As can be seen from the figure, the fluorescence intensity of the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial decreases with increasing dissolved oxygen concentration, indicating that the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial has responsive characteristics to dissolved oxygen in seawater. Therefore, the SiO2@ZnO-NH2 quantum dot fluorescent nanomaterial provided by this invention can be used in the field of dissolved oxygen detection in seawater.

[0073] Comparative Example 1

[0074] The preparation method of Comparative Example 1 is the same as that of Example 1, the main difference being that: no APTEs were added for surface modification of SiO2 and -NH2 groups, and the purification of ZnO quantum dots first used n-hexane to generate a precipitate, and then used anhydrous ethanol for centrifugation and washing.

[0075] Figure 7 The image shows the fluorescence emission spectrum of the ZnO quantum dot fluorescent nanomaterial prepared in Comparative Example 1 without the addition of APTEs under 365 nm excitation. As can be seen from the figure, the fluorescence emission of the ZnO quantum dots is located at approximately 590 nm.

[0076] Figure 8 The image shows the XRD pattern of the ZnO quantum dot fluorescent nanomaterial prepared in Comparative Example 1 without the addition of APTEs. As can be seen from the figure, the diffraction peaks of the ZnO quantum dot fluorescent nanomaterial are consistent with the standard XRD pattern of hexagonal wurtzite zinc oxide (JCPDS No. 36-1451), indicating the successful preparation of ZnO quantum dots.

[0077] Figure 9 The images show the ZnO quantum dot fluorescent nanomaterials prepared in Comparative Example 1 without the addition of APTEs within the pH range of 6.80–10.26 (under UV light). As can be seen from the images, the fluorescence emission intensity of the ZnO quantum dots is not affected, indicating their stability in an alkaline environment.

[0078] Figure 10 The images show ZnO quantum dot fluorescent nanomaterials prepared in Comparative Example 1 without the addition of APTEs dispersed in solutions of different ion concentrations under UV light irradiation. As can be seen from the images, in Cl... - SO4 2- Under certain conditions, ZnO quantum dot solutions exhibit sedimentation due to the lack of protection from the SiO2 shell. - The interaction with ZnO quantum dots leads to aggregation and precipitation, making it impossible to use ZnO quantum dots for the detection of dissolved oxygen in seawater.

[0079] Comparative Example 2

[0080] The preparation method of Comparative Example 2 is the same as that of Example 1, except that 0.08 mL of APTEs solution was added to 0.4 mL of deionized water to prepare an APTEs aqueous solution.

[0081] Figure 11 The figure shows the fluorescence emission spectrum of the ZnO-NH2-a quantum dot fluorescent nanomaterial prepared in Comparative Example 2 under 365 nm excitation. As can be seen from the figure, the fluorescence emission of the ZnO-NH2-a quantum dot fluorescent nanomaterial is located at around 560 nm, which is nearly 10 times higher than that of the ZnO quantum dots in Comparative Example 1.

[0082] Figure 12 The image shows the XRD pattern of the ZnO-NH2-a quantum dot fluorescent nanomaterial prepared in Comparative Example 2. As can be seen from the image, the diffraction peaks of the ZnO-NH2-a quantum dot fluorescent nanomaterial are consistent with the standard XRD pattern of hexagonal wurtzite zinc oxide (JCPDS NO. 36-1451). The diffraction peak at approximately 23° indicates the presence of amino groups on the surface of the ZnO-NH2-a quantum dot fluorescent nanomaterial.

[0083] Figure 13 The figure shows the fluorescence emission spectrum (excitation wavelength 365 nm) of the ZnO-NH2-a quantum dot fluorescent nanomaterial prepared in Comparative Example 2 in the pH range of 6.8–10.26. The inset is a photograph under UV light irradiation. As can be seen from the figure, the ZnO-NH2-a quantum dot fluorescent nanomaterial is stable in an alkaline environment, and its fluorescence emission intensity is not affected.

[0084] Figure 14 The images show the ZnO-NH2-a quantum dot fluorescent nanomaterials prepared in Comparative Example 2 dispersed in solutions of different ion concentrations under a UV lamp. As can be seen from the images, in Cl... - Under certain conditions, the ZnO-NH2-a quantum dot fluorescent nanomaterial solution exhibits sedimentation. This is because the amount of APTEs is too small. Although a SiO2 shell was added for protection, some exposed ZnO quantum dots still react with Cl. - The interaction leads to aggregation and precipitation, therefore it is necessary to control the SiO2 shell concentration to realize the application of ZnO-NH2-a quantum dot nanofluorescent materials in seawater dissolved oxygen detection.

[0085] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. Application of SiO2@ZnO-NH2 quantum dot nanofluorescent material in detection of seawater dissolved oxygen concentration, characterized in that, The SiO2@ZnO-NH2 quantum dot nanometer fluorescent material has a core-shell structure with ZnO-NH2 quantum dots as a core layer and SiO2 as a shell layer; wherein the SiO2@ZnO-NH2 quantum dot nanometer fluorescent material is of a hexagonal wurtzite structure, has a particle size distribution of 2.25-5.25 nm, and has an average particle size of 3.39±0.03 nm; The fluorescent emission of the SiO2@ZnO-NH2 quantum dot nanometer fluorescent material is located at 550-560 nm.

2. Use according to claim 1, characterized in that, The preparation method of the SiO2@ZnO-NH2 quantum dot nanometer fluorescent material comprises the following steps: (1) dissolving a base in anhydrous ethanol to obtain an ethanol solution of the base; dissolving zinc acetate in anhydrous ethanol and transferring to an ice water bath for cooling to obtain an ethanol solution of zinc acetate; (2) adding the ethanol solution of the base drop by drop into the ethanol solution of zinc acetate and stirring until the mixed solution is clear to obtain a ZnO quantum dot solution; (3) adding an aqueous solution of 3-aminopropyl triethoxysilane to the ZnO quantum dot solution and continuously stirring to realize SiO2 coating on the surface of the fluorescent material through an amino functionalization process, and then centrifuging and washing to obtain the SiO2@ZnO-NH2 quantum dot nanometer fluorescent material.

3. Use according to claim 2, characterized in that, The base is potassium hydroxide, sodium hydroxide or lithium hydroxide; and the purity of the base is ≥95%.

4. Use according to claim 2, characterized in that, The base is dissolved in anhydrous ethanol in an ultrasonic-assisted manner; the ultrasonic power is 80-100 W, and the ultrasonic time is 0.5-2 hours.

5. Use according to claim 2, characterized in that, The purity of the zinc acetate is ≥99.995%; the zinc acetate is dissolved in anhydrous ethanol by a heating reflux method; the temperature of the heating reflux is 60-80°C, and the time of the heating reflux is 20-40 minutes; The time for transferring the zinc acetate dissolved in anhydrous ethanol to the ice water bath for cooling is controlled to be 1-5 minutes.

6. Use according to claim 2, characterized in that, In the ethanol solution of the base, the mass ratio of the base to anhydrous ethanol is controlled to be (0.098-0.13):1; in the ethanol solution of zinc acetate, the mass ratio of zinc acetate to anhydrous ethanol is controlled to be (0.03-0.05):1; and the dosage ratio of the ethanol solution of the base to the ethanol solution of zinc acetate is controlled to be 3.4-3.552 g:0.7-24.8 g.

7. Use according to claim 6, characterized in that, In the ethanol solution of the base, the mass ratio of the base to anhydrous ethanol is controlled to be 0.124:1; in the ethanol solution of zinc acetate, the mass ratio of zinc acetate to anhydrous ethanol is controlled to be 0.046:1; and the dosage ratio of the ethanol solution of the base to the ethanol solution of zinc acetate is controlled to be 3.4-3.5 g:0.7-1.2 g.

8. The use according to claim 2, characterized in that, In the aqueous solution of 3-aminopropyl triethoxysilane, the volume ratio of deionized water to 3-aminopropyl triethoxysilane is controlled to be 5:1; and the volume ratio of the aqueous solution of 3-aminopropyl triethoxysilane to the ZnO quantum dot solution is controlled to be (0.018-0.7):

1.

9. Use according to claim 8, characterized in that, The volume ratio of the aqueous solution of 3-aminopropyl triethoxysilane to the ZnO quantum dot solution is controlled to be 0.07:

1.

10. The use according to claim 2, characterized in that, The time for adding the 3-aminopropyl triethoxysilane aqueous solution into the ZnO quantum dot solution under continuous stirring is 20-30 minutes; the centrifugal speed is 6000-10000 revolutions per minute, and the centrifugal time is 3-10 minutes.

Images